In many species of Abies (e.g.
Abies smithiana extends into Afghanistan; Abies webbiana forms dense forests at altitudes of 8000 to 12,000 ft., and ranges from Bhutan to Kashmir; several junipers and the common yew (Taxus baccata) also occur.
Pinus and Picea) - in which the cone-scales persist for some time after the seeds are ripe - the cones hang down and so facilitate the fall of the seeds; in Cedrus, Araucaria and Abies the scales become detached and fall with the seeds, leaving the bare vertical axis of the cone on the tree.
The commonest firs are Abies nordmannia and A.
On the alpine range itself and its immediate branches, at a height of 6000 to 10,000 ft., we have abundant growth of large forest trees, among which conifers are the most noble and prominent, such as Cedrus Deodara, Abies excelsa, Pinuslongifolia, P. Pinaster,P. Pinea (the edible pine) and the larch.
The trees most commonly found are the plane, poplar, maple, walnut, oak, the Cupressus funebris, and various varieties of the genera Pinus, Abies and Larix.
In the wood of Cypressus, Cedrus, Abies and several other genera, parenchymatous cells occur in association with the xylem-tracheids and take the place of the resin-canals of other types.
Of the Abies group, the silver fir (A.
In the North American area Picea alba, P. nigra, Larix americana, Abies balsamea (balsam fir), Thuja canadensis (hemlock spruce), Pinus Strobus (Weymouth pine), Thuja occidentalis (white cedar), Taxus canadensis are characteristic species.
Of the Coniferae, Podocarpus and Pinus longifolia alone descend to the tropical zone; Abies Brunoniana and Smithiana and the larch (a genus not seen in the western mountains) are found at 8000, and the yew and Picea Webbiana at 10,000 ft.